Compositions containing polymers of ethylenically unsaturated monomers in polyisocyanates are described in U.S. and foreign patents and patent publications. Such prior art compositions have found little, if any, use commercially because of any one of many difficulties notably instability, excessive particle size, very high viscosity or the inability when reacted with active hydrogen-containing compounds to provide improved properties, e.g., high modulus to the resulting polyurethanes in those cases where the polymers were dissolved in or reacted with the polyisocyanate. In those instances where dispersions of the polymer in the polyisocyanate did result, the dispersions were relatively unstable and lacked sufficient usefulness in most modern techniques of polyurethane manufacture. A significant development in providing stable polymer/polyisocyanate dispersions is disclosed in U.S. Patent application Ser. No. 135,397, filed Mar. 31, 1980. This application discloses the preparation of stable polymer/polyisocyanate dispersions having beneficial utility in most modern techniques of polyurethane manufacture.
Polymer/polyol dispersions have been and currently are being used in the production of polyurethane products by mixing with polyisocyanates and other polyurethane-forming reagents and reacted to form the polyurethane product and serve as a convenient, efficient and economical means for improving resultant polyurethane properties. This procedure and the resulting polymer/polyol dispersions have been widely accepted by the polyurethane industry and continue to be extensively used throughout the industry.
As mentioned above, prior attempts have been made to make polymer dispersions in polyisocyanates and to use such dispersions in the manufacture of polyurethanes by reaction with active hydrogen compounds. It is believed that these attempts have met with little or no commercial success for a variety of reasons. With the exception of polymer/polyisocyanate dispersions disclosed in U.S. Patent application Ser. No. 135,397, filed Mar. 31, 1980, polymer/polyisocyanate dispersions obtained pursuant to the prior art teachings had very high viscosities at desirable polymer concentrations to be commercially feasible. The development of more sophisticated, higher speed and larger volume equipment, machines and systems for handling, mixing and reacting the polyurethane-forming ingredients have created the need for improvement in polymer/polyisocyanate, polymer/polyol and other dispersions used. The need for more stable dispersions has developed so that they can be stored until used without undergoing any significant settling or separation. Another criterion imposed by sophisticated equipment is the need for small particle sizes because large particles tend to damage the pumps employed in such equipment.
At one time there was not much concern for the viscosity or filterability of the polyurethane-forming reactants, i.e., the polymer/polyol and other dispersions in actual commercial practice. However, the state of the art of polyurethane production now has advanced to the point where these considerations are very important. There is now much concern with filterability and viscosity because of the more sophisticated machine systems now in use for large volume production. Also, the prior art dispersions could not be made in highly stable condition with the relatively low molecular weight polyisocyanates, thus rendering the lower molecular weight materials less desirable than the higher molecular weight materials as a component of the dispersions. The lower molecular weight materials, however, are of value in those instances where low viscosity is essential and for foams, coatings, adhesives and some types of sealants.
The present invention provides highly stable and highly filterable polymer/polyisocyanate compositions having low viscosity and beneficial utility in the manufacture of polyurethane products. It provides better dispersion stability than can be obtained by earlier procedures and eliminates or minimizes the expenses and hazards or difficulties accompanying some of the earlier techniques. The present invention also provides means for providing highly stable or reasonably stable polymer/polyisocyanate compositions having high polymer contents and the production of polyurethanes having improved physical properties. It also permits a wider selection of polyisocyanates and polymer contents to be used in the manufacture of stable polymer/polyisocyanate compositions. It also permits the use of polyisocyanates of lower viscosities to make polymer/polyisocyanate compositions with higher polymer contents in the dispersion without impairing stability. These and other advantages are obtained by polymerizing at least one ethylenically unsaturated monomer in situ in a blend of an organic polyisocyanate and a stabilizer.
Nowhere in the prior art currently known to us is there any disclosure or suggestion of the discovery of the advantages of the present invention in polymerizing at least one ethylenically unsaturated monomer in situ in a blend of an organic polyisocyanate and a stabilizer to form stably dispersed polymer particles in the organic polyisocyanate. U.S. Pat. No. 3,968,089 discloses the polymerization of ethylenically unsaturated monomers in a polyol-polyisocyanate prepolymer. U.S. Pat. No. 3,422,165 discloses polymer/polyisocyanate complex compositions formed by polymerizing ethylenically unsaturated monomers in polyisocyanates and also discloses the production of polyurethanes from such complex compositions. British Pat. No. 1,447,273 discloses polymer/polyisocyanate compositions formed by the polymerization of at least one ethylenically unsaturated monomer in an isocyanate. However, none of these prior art references and no prior art is currently known to us which discloses, teaches or suggests stable polymer/polyisocyanates having the advantageous properties of the compositions of this invention prepared by polymerizing at least one ethylenically unsaturated monomer in a blend of an organic polyisocyanate and a stabilizer as claimed and described herein.